Solid state light sources are increasingly used in lighting because of their energy efficiency and continually decreasing costs. The use of solid state light sources in lighting is generally disclosed in the following: U.S. Pat. No. 6,773,139 (Sommers); U.S. Pat. No. 6,814,463 (Mele); and U.S. Patent Application Publication No. 2008/0019130 (Wang).
White light may be produced from solid state light sources in a variety of ways. For example, one or more solid state light sources may be mounted on a substrate, such as but not limited to a printed circuit board. The one or more solid state light sources, which typically emit light of a wavelength that produces a blue color, may be covered with a phosphor and/or a mixture of phosphors, either directly within the package or remotely, to provide phosphor conversion of the light emitted from the underlying one or more solid state light sources to produce white light. Alternatively, combinations of two or more different “colors” (i.e., wavelengths of light corresponding to distinct colors) of light may be mixed together to produce white light. Color-mixing is disclosed in the following: U.S. Pat. No. 7,431,477 (Chou); U.S. Pat. No. 8,174,189 (Kim); U.S. Pat. No. 8,096,675 (Posselt); U.S. Pat. No. 8,368,315 (Gaines); U.S. Patent Application Publication No. 2012/0287620 (Guerrieri); and U.S. patent Application Publication No. 2013/0088142 (Allen).
Although the technique of color mixing using different color solid state light sources on a printed circuit board (PCB) is known, there have been challenges to provide uniform and efficient color mixing when more than two color LEDs are adjacent to each other. These challenges include resolving color separation due to different color LEDs on the PCB and improving light output uniformity without using additional optics. Mounting different color LEDs on a PCB also presents other challenges with weak heat dissipation and a complicated circuit design.